A spiritual leader or religious leader, also sometimes known as a cleric, was a member of the leadership of a religion, such as a priest or preacher.
Alar was the religious leader of the Skorr, sometime during the mid-21st century. Alar was viewed by many of his people as "our salvation and our teacher", as he brought them peace, made them civilized. Prior to is death, he was made "immortal", when his brain patterns were recorded in a piece of indurite sculpture, known as the Soul of the Skorr. When the Soul was stolen in 2269, the Skorr became infuriated and prepared for a jihad against the known galaxy. (TAS: "The Jihad")
Pri'Nam D'Jamat, who lived during the 2150s, was a spiritual leader among certain members of the Triannons, such as Yarrick, who was willing to "follow him to [his own] death." (ENT: "Chosen Realm")
Originally, the spiritual leader of the Bajorans was known as the kai, who attended to "millions". (DS9: "Emissary", "The Reckoning") However, those in positions below kai, such as vedeks, were also considered spiritual leader. (DS9: "In the Hands of the Prophets", "Resurrection") When Benjamin Sisko came to be known as the Emissary of the Prophets, it was seen as a role the kai was forced to share with Sisko, who was revered as a religious figure, causing great bitterness, especially with Kai Winn. To worsen matters, because Sisko, the Emissary, was an "outsider, a non-Bajoran," it was something the kai could never forgive him for being. (DS9: "The Reckoning", "The Visitor", "Accession") In 2371, Kai Winn was both the spiritual leader and political leader, or First Minister of Bajor, a title she held during the interim between Kalem Apren and Shakaar Edon. (DS9: "Shakaar") In 2374, Bareil Antos, of the mirror universe, found it amusing that his deceased counterpart was a religious leader, after it was explained to him why Bajorans of the prime universe kept staring at him. (DS9: "Resurrection")
Klingon clerics were present on Boreth. Worf visited them after the destruction of the Enterprise in 2371. (DS9: "The Way of the Warrior", "The Sword of Kahless")
The rank of High Cleric also existed on Boreth, and the term cleric might have been used interchangeably with it. This is particularly the case in The Sword of Kahless, where Kor referenced the plot in "Rightful Heir" by saying ambitious clerics had cloned Kahless.
A magistrate, representing the Nechani, met Captain Kathryn Janeway's plea to save Kes, after she wandered into a sacred shrine and was hit by an energy beam that placed her in a coma and near death, by explaining that he was "caught in a most difficult situation," due to the fact that he was "an official of the government, not a spiritual leader," and as such, he didn't "pretend to understand why [their] spirits do what they do." (VOY: "Sacred Ground")
Dala and Mobar posed as clerics (as a Sister and Brother respectively) from Selnia Prime when they met Neelix and Tom Paris on the planet in 2376. (VOY: "Live Fast and Prosper")
Monean clerics believed that The Waters was a divine gift from the creators. (VOY: "Thirty Days")
According to The Doctor, the sentient hologram, Iden, "[a]pparently [..] sees himself as some kind of spiritual leader, and he's trying to enlarge his flock," by liberating other holograms from servitude. (VOY: "Flesh and Blood")